Abstract
We investigate the cooperation efficiency of the multiple-relay channel when carrier-level synchronization is not available and all nodes use a decode-forward scheme. We show that by using decode-forward relay signaling, the transmission is effectively interference-free even when all communications share one common physical medium. Furthermore, for any channel realization, we show that there always exist a sequential path and a corresponding simple power allocation policy, which are optimal. Although this does not naturally lead to a polynomial algorithm for the optimization problem, it greatly reduces the search space and makes finding heuristic algorithms easier. To illustrate the efficiency of cooperation and provide prototypes for practical implementation of relay-channel signaling, we propose two heuristic algorithms. The numerical results show that in the low-rate regime, the gain from cooperation is limited, while the gain is considerable in the high-rate regime.
Highlights
A wireless ad hoc network is an infrastructureless network, in which the communications between two nodes are typically maintained by the cooperation of other nodes
The essential difference between the traditional multihopping and the relaychannel signaling is that in the latter, a node uses the information from all its upstream nodes instead of the information from the closest one
The relay channel was first introduced by van der Meulen [1, 2]
Summary
A wireless ad hoc network is an infrastructureless network, in which the communications between two nodes are typically maintained by the cooperation of other nodes. An adaptive transmission scheme will allow the source to communicate directly with the destination if the relay has a poor link to the source—one form of routing For delay-insensitive services, the source and the relay may choose to adjust their transmission rate according to the channel condition [7] In many applications such as sensor networks, the nodes typically operate on limited-energy batteries, which are usually not rechargeable or replaceable, and results in severe energy constraints. Assuming that the source-destination pair in the multiple-relay channel wants to maintain a constant communication rate R, we define an outage event for a given transmission scheme T and the channel realization H as.
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